National University of Science and Technology «MISiS», 119049, Moscow, Russia.
Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, IZMIRAN, 142190, Troitsk, Moscow, Russia.
Sci Rep. 2018 Jan 19;8(1):1224. doi: 10.1038/s41598-017-18162-8.
Magnetic vortices existing in soft magnetic nanoparticles with sizes larger than the single-domain diameter can be efficient nano-heaters in biomedical applications. Using micromagnetic numerical simulation we prove that in the optimal range of particle diameters the magnetization reversal of the vortices in spherical iron and magnetite nanoparticles is possible for moderate amplitudes of external alternating magnetic field, H < 100 Oe. In contrast to the case of superparamagnetic nanoparticles, for the vortex configuration the hysteresis loop area increases as a function of frequency. Therefore, high values of the specific absorption rate, on the order of 1000 W/g, can be obtained at frequencies f = 0.5-1.0 MHz. Because the diameter D of a non single-domain particle is several times larger than the diameter d of a superparamagnetic particle, the volume of heat generation for the vortex turns out to be (D/d) times larger. This shows the advantage of vortex configurations for heat generation in alternating magnetic field in biomedical applications.
在尺寸大于单畴直径的软磁纳米粒子中存在的磁涡旋可以成为生物医学应用中的高效纳米加热器。通过微磁数值模拟，我们证明在最佳粒径范围内，对于适中幅度的外部交变磁场，H < 100 Oe，铁和磁铁矿纳米粒子中的涡旋的磁化反转是可能的。与超顺磁纳米粒子的情况相反，对于涡旋结构，磁滞回线面积随频率增加。因此，在频率 f = 0.5-1.0 MHz 时，可以获得高达 1000 W/g 量级的高比吸收率。由于非单畴粒子的直径 D 是超顺磁粒子的直径 d 的几倍，因此用于涡旋的发热体积是 (D/d) 倍。这表明在生物医学应用中，交变磁场中涡旋结构用于发热具有优势。
